Heating of hydrocarbon fluids



Jan. 26, 1954 v MEKLER HEATING. OF HYDROCARBON FLUDS Filed OCT.. l, 1949 Patented Jan. 26, 195.4

UNITED STATES PATENT OFFICE.

HEATING OF HYDROCARBON FLUDS Valentine Mekler, Jackson Heights, N. Y., as-

signor to The Lummus Company, New York, N. Y., a corporation of Delaware Application October 1, 1949, Serial No. 119,076

1l Claims. l

This invention relates to improvements in the art of heating hydrocarbon fluids predominantly by radiant heat applied to banks of tubing through which a charge of the fluid is passed within a furnace chamber. More particularly, the invention is concerned with improved performance of pyrolysis of light hydrocarbon gases to obtain desired olens as, for example, the cracking of ethane or propane to obtain ethylene. A temperature of around 1400 F. is required for such cracking and, in applying the required heat to the tubing which contains the charge, much care must be taken to obtain a proper rate of heat input along the course of the charge, prevent objectionable coke deposit within the tubing and also avoid damage to the tubing by overheating. U. S. Patent No. 2,456,786 of Ludwig Kniel et al. and U. S. Patent No. 2,456,787 of Ludwig Kniel disclose methods and apparatus devised particularly for performance of such cracking. The present application is directed to improvements over the disclosures of said patents.

An important object of the invention is to provide for more flexible control of heat input to the course of the charge so that a desired temperature curve may be obtained more readily.

A further object of the invention is to provide for adequate heating of a cracking portion of the course while protecting other portions of the course from overheating and damage to the tubmg. x

l A still further object is to provide a heating apparatus embodying an improved combination and arrangement of tube banks, burners and shield means devised to afford the desired flexible control of heat input and also protect the tubing from overheating.

Further objects and advantages will appear from the following description and the accompanying drawings.

In the drawings:

Fig. 1 is a vertical transverse section of a furnace embodying the invention;

Fig. 2 is a horizontal section, on a reduced scale, taken on the line 2-2 of Fig. 1, a portion of the furnace being broken away and some details of the wall structure being omitted; and

Fig. 3 is a diagrammatic view showing a modified arrangement of the tubing.

According to the invention, the lcharge to be heated is passed in separate streams through a pair of tube banks located along oppositeside walls 'of a furnace chamber. Then, the fluid is passed from said side banks through a bank of tubes lying within a plane intermediate said side banks. Combustion is conducted within V*outer regions of the chamber adjacent theside banks and within inner regions at opposite sides of said intermediate bank to preheat the charge within the side banks predominantly by radiant heat and further heat the charge within the intermediate bank. predominantly by radiant heat, to conversion temperature. overheating of the side banks is prevented by the shielding effect of walls which separate said inner and outer combustion regions. These walls protect the side banks from the heat of combustion within said inner regions which raises the charge with-n the intermediate bank to conversion temperature. Provision is also made for conducting combustion within addi tional regions of the furnace chamber located at opposite sides of the said intermediate plane and outwardly of said shield walls and said inner and outer combustion regions for additional radiant heat input to tubing within said plane. In one form of the invention, the tubing in said plane includes, in addition to the cracking bank, a preliminary heating bank through which the charge is passed en route to the side banks. This preliminary bank is heated by radiant heat from the combustion within said additional regions. Combustion gases are passed from the inner and outer regions into said additional regions and escape through an outlet from the latter. v

Referring to Figs. 1 and 2a furnace chamber l is formed by a oor or hearth 2, opposite side walls 3 and vertical ends walls 4. Lower portions 3a of the side walls 3 are vertical and upper portions 3b thereof converge upwardly to an outlet flue 5 located in a vertical central plane of the furnace. All of said walls are constructed of blocks or slabs 6 of refractory material sheathed with heat insulation 7. Columns 8 support the furnace chamber elevated from the ground or from a foundation.

Within the furnace chamber a pair of outer tube banks 9 are supported in vertical planes adjacent the vertical portions 3a of the respective side walls. A pair of intermediate tube banks l 0 and I i are supported, one above the other, within the vertical central plane of the chamber. Each of the four tube banks comprises a single vertical row of spaced horizontal tubes all in a vertical plane and serially connected by return bends for ow of the charge in a serpentine course through all of the tubes of the bank in succession. A charge delivery pipe I2 leads tothe uppermost tube of the upper central bank I and two transfer pipes I3 lead from the lowermost tube of the bank lo to the uppermost tubes of the side banks side banks, the tubes of the central banks are of bridge walls 2Iii .of refractory material extend upwardly from the 'hearth 2, at opposite sides of the bank II. These walls are located approximately midway between the bank I I and the side banks 9 and they extend above the topmo'st level of the latter. As shown, the central bank II may extend above the level `of the4 upper edges.

of the bridge walls. Beneath the banket ,and

II there are also narrow horizontal refractory shield walls I1. extend from end to end of the furnace chamber.

At the bottom of the furnace chamber there are four rows of burners arranged to re upwardly through ports Vin the hearth 2. The burners I8 of two of said rows are arranged re.- spectively, to conduct combustion within the re gions between the bridge Walls I6 and the side banks 9. The burners I9 of the other two rows are arranged to conduct combustion within the regions at opposite sides ofthe bank II and be:

tween sameand the walls I6. A t opposite sides of the upper central bank ID there are two, horizontal'rows of burners 29 arranged to nre laterally inwardly through flared ports 2I in the sidewalls of the furnace chamber. Thereby, combustion may be conducted within regions at opposite sides of the bank Il). The burners 2g are mounted, as; at 22, for vertical angular adf The walls I6 and the walls I'I,

justment, Vand they are spaced substantially above the level of the upper edges of the bridge walls I6. The burners I8, I9 and 29 are provided withY valves 23 for combustion control. These valves maybe either individual to the burners or individual tothe diierent rows of burners so that combustion within the different regions may be controlled independently.

In the operation of thefurnace just described,

the charge, which may be a hydrocarbon gas such as ethane orpropane,)for example, is introduced through the delivery pipe I2 andjpassed downwardly through the bank I which consti,-Y tutes a preliminary heating, bank. Within this bank Vthe charge which may be relatively cold upon` introduction is preheated by radiant heat from the combustion conducted by the side burners 2G and from combustion gases rising past the opposite sides of the bank? from all of the combustion'regions ofthe chamber'to the outlet which leads to a-stack, not shown. Heat lis also reradiated to opposite* sides of the bank I0 by the converging walls 3b. At the lower end of the bank vI the charge is Split and passed through thel transfer pipes I3V andi downwardly through the'side banks 9. Within the side banks, f

the charge is 'further preheated, predominantly by radiantheat, through combustion conducted by the burners I8 and byreradiation from the walls I 6. The walls I'I at the bottom ofthe banks 9 serve. as shields to prevent overheating of the lower tubes of the banks. The charge, preheated within the tube banks I0 and 9, is passed through the transfer pipes I4 and downwardly; through the bank II kwhich constitutes a conversion or cracking bank.- This bank is heated predominantly by radiant heatr from combusof the charge within their-bank -II .may be had without risk of overheatingand damaging of the tubing of the preheating banks owing to the provision of the walls I 6 which separate the preheating regions of combustion from the conversion lregions of combustion and shield the tubes 0f the banks 9. That renders it possible to employV less .expensive tubing in the preheating banks than in the conversion banks whose tubes require an alloy aifording high heat resistance. The separation ofthe combustion regions and the,` arrangement of the tube banks and the independently controllable burners also provide a high .degree of flexibility inthe control of heat input to the charge in its course through the tubing and facilitate the obtaining of a desired heat curve. The adjustability of the burners 29 renders it possible to direct them toward either the bank I0 or the upper portion of the conversion bank I I for selective heat input.V

In the form of the invention shown in Fig. 3

the furnace walls, the side tube` banks 9, the

bridge walls I6 and the burners, here indicated by arrows, are all in an arrangement` similar to that shown in Fig. 1. The bank I0, however, is omitted 'and the central conversion bank, here designated I Ia, is extended upwardly to take the place of the omitted bank. The chargeis introduced in rseparate streams, through pipes I2a, to the respective side wall banks 9', andA transfer pipes I4@ lead from the lowermost tubes of said banks to the uppermost Vtube of the central bank IIa. The charge in its downward passage through the bank IIe is heatedpredominantly by radiant heat from combustion .conducted by the burners V2li and I9 in succession andv is also heated by reradiation from thewalls 3b and from combustion gases rising pastthe bank to the outlet 5. As in the iirst form ofthe invention', provision is made for prevention, of overheating of the preheati'ng tubing, independent control of combustion withinrthe different4 regions and'substantially uniform distribution of heat around the circumference of the tubes of the conversion bank. ,Such distribution of heat around the cross section ofv the individual tubes prevents cold spots upon which coke will accumulate. A

It 1s, of course, to be understood that the present disclosure of myinvention is merely illustrative and in nowise limiting and that the in- Vention comprehends such modifications as will comewithin the scope of the claims.

I claimsl. A heater for hydrocarbon fluid, comprising a furnace chamber, a pair of banks of preheating tubes within said chamber and adjacent opposite walls thereof, a Vbank of advanced heating tubes extending between saidj preheating banks in a plane intermediate the latter, burners disposed to conduct combustion within regions between said bank of advanced heating tubes and said ypreheating banks and in direct exposure to the respective banks to heat all of said banks predominantly byv radiant'heat, a bank of preliminary heating tubes within thefurnace chamber and in saidrinte'rmediate plane and beyond said preheating tubes, burners disposed to conduct combustion within regions at opposite sides of said preliminary heating bank and in direct exposure thereto for radiant heating of same, each of said four banks having an inlet and an outlet for, the fluid, conduits connecting the outlet of saidV preliminary heating bankY to theinlets of said preheating banks. to pass the fluid thereto,` and conduits connecting the outlets of the preheating banks to the inlet lof saidadvanced heating bank therebetween to pass the fluid thereto. V2. The heater claimed in claim 1 wherein the said burners for conducting combustion at opposite sides of the said preliminary heating bank are directed inwardly toward the said plane and are mounted for angular adjustment with reference to the plane.

3. A heater for hydrocarbon fluid, comprising a furnace chamber, a pair of banks of preheating tubes within said chamber and adjacent the side walls thereof, a bank of advanced heating tubes extending between and beyond said preheating banks in a plane intermediate the latter, each of said banks having an inlet and an outlet for the liuid, conduits leading from the outlets of the preheating banks to the inlet of said bank of advanced heating tubes to pass therethrough the fluid from both of said preheating banks, walls between the bank of advanced heating tubes and the prehating banks and dividing the chamber into outer combustion regions at the inner side of the preheating banks and inner combustion regions at opposite sides of the bank of advanced heating tubes and separated thereby, burners disposed to conduct combustion within all of said regions in direct exposure to the respective banks to control independently the combustion within said inner and outer regions, said dividing walls serving to shield the preheating banks from the heating effects of the combustion within said inner regions, and burners disposed to conduct combustion within regions of the chamber at opposite sides of said intermediate plane and adjacent the portion of the bank of advanced heating tubes which extends beyond the preheating banks, for radiant heating of said bank portion, said last-mentioned burners being directed toward said plane and mounted for angular adjustment with reference to said plane.

4. A heater for hydrocarbon fluid, comprising a furnace chamber, a pair of banks of preheating tubes within said chamber and adjacent opposite walls thereof, a bank of advanced heating tubes extending between said preheating banks in a vertical plane intermediate the latter, each of said three banks having an inlet and an outlet for the fluid, conduits leading from the outlets Y walls between the bank of advanced heating tubes and the preheating banks and dividing the chamber into outer combustion regions at the inner side of the preheating banks and inner combustion regions at opposite sides of the bank of advanced heating tubes and separated thereby, burners disposed to conduct combustion within all of said regions in direct exposure to the respective banks to control independently the combustion within said inner and outer regions, said dividing walls serving to shield the preheating banks from the heating effect of the combustion within said inner regions, a bank of preliminary heating tubes within the chamber and located within said plane, above the bank of advanced heating tubes and beyond said inner combustion regions and having an inlet and an outlet for said fluid, conduits connecting the outlet of said bank with the inlets of both of said preheater banks for delivery of the fluid thereto, and burners disposed to conduct combustion Within regions of the chamber at opposite sides of the bank of preliminary heating tubes to heat same by radiant heat, the said inner and outer regions opening into said regions at opposite sides of the bank of preliminary heating tubes and the chamber having gas outlet means opening from the last-mentioned regions.

5. The method of heating a hydrocarbon fluid. comprising passing said fluid in a confined stream along a preliminary heating course, conducting the fluid from said course in a pair of confined streams along a pair of transversely opposed spaced preheating-courses, conducting the fluid from both of said courses in a single confined stream along an advanced heating course extending in a plane between said preheating courses, said preliminary heating course being in a position oifset in said plane from said advanced heating course, conducting combustion within outer regions between said advanced course and said preheating courses and in direct exposure to the latter respectively to heat same predominantly by radiant heat, conducting combustion within inner regions between said preheating courses and said advanced course and in direct exposure to opposite sides of the latter Ato further heat the -iiuid in the advanced course predominantly by radiant heat, shielding the preheating courses frorn the heating effect of the combustion within said inner regions, conducting additional combustion within regions at opposite sides of said preliminary heating course and in direct exposure thereto for radiant heating thereof, and conducting combustion gases from all of the said combustion steps through the lastmentioned regions.

6. The method of heating a hydrocarbon fluid, comprising passing said fluid in a pair of confined streams along a pair of transversely op posed spaced preheating courses, conducting the fluid from both of said courses in a single conned stream along an advanced heating course extending in a plane between said preheating courses, conducting combustion Within outer re` gions between saidadvanced heating course andv said preheating courses and indirect exposure to the latter respectively to heat same predominantly by radiant heat, conducting combustion within inner regions between said preheating courses and said advanced course and in direct exposure to opposite sides of the latter to further heat the fluid in the advanced course predominantly by radiant heat, shielding the preheating courses from the heating eiect of the combustion within said inner regions, and conducting additional combustion within regions spaced from said inner and outer regions and at opposite sides of and in exposure to said advanced heating course for radiant heating thereof.

'7. A heater for hydrocarbon fluid, comprising a furnace chamber, a pair of banks of preheating tubes within said chamber and adjacent the op- -posite walls thereof,a bank of advanced heating tubes extending between said preheating banks in a plane intermediate the latter, each of said three banks having an inlet and an outlet for the fluid, conduits leading from the outlets of the preheating banks to the inlet of said bank of advanced heating tubes to pass therethrough the fluid from both of said preheating banks, walls between the bank of advanced heating tubes and the preheating banks and dividing the Ychamber into outer combustion regions at the inner side of the preheating banks and inner combustion regions at opposite sides of the bank of advanced heating tubes and separated thereby, burners disposed to conduct combustion within all of said regions in direct exposure to the respective banks to control independently the combustion within said inner and outer regions, said 

1. A HEATER FOR HYDROCARBON FLUID, COMPRISING A FURNACE CHAMBER, A PAIR OF BLANKS OF PREHEATING TUBES WITHIN SAID CHAMBER AND ADJACENT OPPOSITE WALLS THEREOF, A BANK OF ADVANCED HEATING TUBES EXTENDING BETWEEN SAID PREHEATING BANKS IN A PLANE INTERMEDIATE THE LATTER, BURNERS DISPOSED TO CONDUCT COMBUSTION WITHIN REGIONS BETWEEN SAID BLANK OF ADVANCED HEATING TUBES AND SAID PREHEATING BANKS AND IN DIRECT EXPOSURE TO THE RESPECTIVE BANKS TO HEAT ALL OF SAID BANKS PREDOMINANTLY BY RADIANT HEAT, A BANK OF PRELIMINARY HEATING TUBES WITHIN THE FURNACE CHAMBER AND IN SAID INTERMEDIATE PLANE AND BEYOND SAID PREHEATING TUBES, BURNERS DISPOSED TO CONDUCT COMBUSTION WITHIN REGIONS AT OPPOSITE SIDES OF SAID PRELIMINARY HEATING BANK AND IN DIRECT EXPOSURE THERETO FOR RADIANT HEATING OF SAME, EACH OF SAID FOUR BANKS HAVING AN INLET AND AN OUTLER FOR THE FLUID, CONDUITS CONNECTING THE OUTLET OF SIAD PRELIMINARY HEATING BANK TO THE INLETS OF SAID PREHEATING BANKS TO PASS THE FLUID THERETO, AND CONDUITS CONNECTING THE OUTLETS OF THE PREHEATING BANKS TO THE INLET OF SAID ADVANCED HEATING BANK THEREBETWEEN TO PASS THE FLUID THERETO. 